Spectroscopic traits of holmium in magnesium zinc sulfophosphate glass host: Judd - Ofelt evaluation

Abstract

Basic understanding on the spectroscopic behaviour of holmium ion (Ho3+) doped in magnesium zinc sulfophosphate glass host is essential for the development of inexpensive and eye–safe infrared solid state laser. To achieve this goal, six such glass samples were prepared using melt quenching method at varying Ho3+ ions contents. FTIR and Raman spectra were recorded to determine the structural properties of the synthesized glasses. Samples were characterized using UV–Vis–NIR absorption and photoluminescence (PL) spectroscopy to determine the Ho3+ ions concentration dependent spectral properties. The absorption spectra of the studied glasses revealed seven peaks which were allocated to the transition from the ground state (5I8) to the excited states (3H6, 5G5, 5G6, 3K8, 5F3, 5F4+5S2, 5F5, 5I6, and 5I7) of Ho3+ ion. Judd–Ofelt (J–O) intensity parameters (Ω2, Ω4, and Ω6) and radiative parameters such as transition probabilities, fluorescence branching ratio, and radiative lifetime were calculated from the measured optical spectra. The nephelauxetic ratio shows negative value signifying ionic bond between REI and the ligand. The value of J–O parameters Ω2, Ω4, Ω6 and spectroscopic quality factor were varied in the range of (4.10 − 8.05) ×10−20 cm2, (1.96−2.77) ×10−20 cm2, (1.95−2.31) ×10−20 cm2 and (1.01 − 1.25), respectively. The small of Ω2 indicated high symmetry around Ho3+ ions while the large value of Ω4 and Ω6 signified the occurrence of high rigidity of the glasses. PL emission spectra of the synthesized glasses disclosed two significant bands assigned to 5F4 → 5I8 (green) and 5F5 → 5I8 (red) transitions. The stimulated emission cross–section for the green and red luminescence was ranged respectively between (8.60 − 10.79) ×10−21 cm2 and (9.35 − 11.62) ×10−21 cm2. The proposed glasses was established to be beneficial for solid state laser application.